This is a competing renewal for a Sexually Transmitted Infections Cooperative Research Center (STI ORG). The Southeastern STI ORG is comprised of six projects Including studies on the sexually transmitted pathogens Neisseria gonorrhoeae and Haemophilus ducreyi. Five synergistic projects explore molecular pathogenesis, immunobiology and possible vaccines for gonorrhea, and the sixth project focuses on development of a promising vaccine for H. ducreyi. The six projects are supported by an Administrative Core, a Microbiology Core and an Immunology Core. Project 1 uses the murine model of gonococcal infection to study mucosal vaccine candidates. Project 2 focuses on iron-regulated adherence factors of N. gonorrhoeae. Project 3 deals with genetic mechanisms of gonococcal resistance to mediators of innate immunity. Project 4 aims at preventing gonococcal infection by targeting the adherence factor PilG. Project 5 centers on innate host immune responses to gonococcal infection. Project 6 focuses on the H. ducreyi outer membrane protein DsrA as a chancroid vaccine using a swine model of infection. The Microbiology Core will conduct experimental human gonococcal infection experiments in support of Projects 2-5. The Immunology Core provides expertise In mucosal adjuvants and immunization protocols for gonococcal studies in mice and chancroid studies in pigs and sophisticated immune monitoring using specimens from animals and humans. The overall theme uniting these projects and cores is New Approaches to STI Prevention. PROJECT 1: Mucosal Vaccines against Gonorrhea (Jerse, A) PROJECT 1 DESCRIPTION (provided by applicant): PROJECT SUMMARY (See instructions): The development of an effective gonorrhea yaccine is challenged by the antigenic variability of the Neisseria gonorrhoeae (Gc) surface and a lack of information on the correlates of protection against infection. Gc porin is a good vaccine candidate based on its abundance in the outer membrane (OM), limited variability, and its roles in epithelial cell invasion and serum resistance via binding to C4bp-binding protein (C4BP) and factor H (fH). Other promising vaccine targets are MtrE, the OM channel of the MtrCMtrD- MtrE active efflux pump, and OmpA, a conserved OM protein that confers adherence to and invasion of human genital tract cells. Our primary objective is to target surface-exposed loops of GC porin in active and passive immunization strategies against gonorrhea. We will also test the protective efficacy of MtrE and OmpA. Specifically, we will 1) characterize Abs against selected porin loops for in vitro and in vivo correlates of protection and the capacity to block C4BP- and fH-binding to serum resistant strains. The bactericidal and opsonophagocytic activity of Abs against cyclic porin peptides will be measured against Gc strains of different porin types. The capacity of Abs to inhibit porin-mediated invasion of human cervical cells and to block the binding of human fH and C4BP to serum resistant Gc will be tested. We will perform passive protection studies with normal, complement- and granulocyte-deficient mice to identify mechanisms of antibody-mediated protection. We will also ii) develop an active immunization strategy based on cyclic porin loop peptides to protect mice from Gc infection. The optimum dose of peptide and type of adjuvant needed to induce high titer serum and mucosal antibodies with anti-Gc activity will be determined. Mice will be immunized with the most promising peptides, and immunized and unimmunized mice will be challenged intravaginally with the homologous Gc strain to determine if immunization affects susceptibility to infection or colonization load. The local and systemic immune response to two peptides that show protection and an analogous peptide that does not will be thoroughly characterized to define correlates of protection, ill.) Finally, we will investigate the protective potential of MtrE and OmpA as vaccine candidates based on their demonstrated importance in experimental murine infection. We will utilize MtrE- and OmpA-specific antibodies to investigate in vitro correlates of protection and perform immunization/challenge studies with purified MtrE, OmpA and surface-exposed regions of these molecules to measure their potential as vaccine antigens against N. gonorrhoeae in vivo.